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22 Two broad concepts have emerged in the management of contaminated land over the past 30 years - the use of risk assessment to determine the seriousness of problems, and the use of risk management to mitigate problems found by risk assessment to be significant (Vegter et al, 2002, and ITRC, 2008). For a risk to be present there needs to be a source of hazardous contamination, one (or more) receptors that could be adversely affected by the contamination, and one or more pathways linking the source to the receptors. Receptors might be human health, water resources, a built construction, or the wider environment. In the UK this combination of a source-pathway-receptor is referred to as a pollutant or contaminant linkage. Requirements for remediation strictly depend on risk management needs, whether the intended use of land is for a ‘hard’ end use, such as a built development or a ‘soft’ end use, where the soil remains unsealed (eg Menger, 2012), such as community parkland. Risk management focuses on breaking the contaminant linkage, by controlling the source (eg extracting the contamination from the subsurface), managing the pathway(s) (eg preventing migration of contamination), protecting the receptor(s) (eg planning controls to avoid sensitive land uses) or a combination of these components. Conventional approaches to contaminated land risk management have focused on containment, cover and removal to landfill. However, since the late 1990s there has been a move towards treatment-based remediation strategies using in situ and ex situ treatment technologies. More recently the concept of ‘gentle’ remediation options (GRO) has emerged. These are risk management strategies/ techniques that result in no gross reduction (or a gain) in soil functionality as well as risk management. They have particular usefulness for maintaining biologically productive soils. GROs encompass a number of technologies that include the use of plant (phyto-), fungal (myco-) or microbiologically-based methods, with or without chemical additives, for reducing contaminant transfer to local receptors by in situ stabilisation (using biological or chemical processes) or extraction of contaminants (eg Ruttens et al, 2006, Grispen et al, 2006, Chaney et al, 2007, Vangronsveld et al, 2009, Onwubuya et al, 2009, and Mench et al, 2010), such as phytovolatilisation, phytodegradation, phytoextraction, rhizofiltration, phytostabilisation and mycoremediation. As a concept GROs are a development of an earlier idea called ‘extensive’ technologies, which sought to distinguish low input longer term remediation approaches from energy and resource intensive strategies (Bardos and van Veen, 1996). Biologically productive soils include those used for agriculture, habitat, forestry, amenity, and landscaping, so GROs will tend to be of most benefit where a ‘soft’ end use of the land is intended. Conventionally regeneration of contaminated land for soft end use has involved the use of cover systems with revegetation and/or removal of contamination hot spots (Cairney and Hobson, 1998). Remediation (ie treatmentbased mitigation of contaminants using biological, chemical or physical processes) has been largely restricted to returning Alternative remediation approaches for brownfield sites* Professor Andrew Cundy, University of Brighton, explains the application of gentle remediation Figure 2 ‘Gentle remediation’ in Saxony, Germany: large scale trials involve poplar and willow growth and coppicing in land contaminated by former mining activity INfrastructure


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